Copper process is a commonly used technology for the current large-size LCD panel products, and usually with 4-mask process to reduce the cost of the array process. However, with the use of 4-mask process, the side surface of the copper will be exposed to the dry etching gas under the process, then the copper compounds are formed to affect the next etching process, and the abnormal taper angle and the serrate data lines are formed to affect the step coverage.
Specifically, the 4 Mask process in the prior art is generally as follows: first wet etching, then dry etching, wet etching again, and last dry etching to obtain the data line and the source/drain. A structural schematic view of a pattern after the first wet etching is as shown in FIG. 1; a structural schematic view of a pattern after the first dry etching is as shown in FIG. 2 and a scanning electron microscope (SEM) diagram is as shown in FIG. 3, the sidewall of copper reacts with gas such as SF6/Cl2 in dry etching to form a copper compound layer 1b; a structural schematic view of a pattern after the second wet etching is as shown in FIG. 4 and a scanning electron microscope (SEM) diagram is as shown in FIG. 5, the existence of the copper compound layer formed above will greatly affect the wet etching of the copper in the next step and finally form a jagged edge; a structural schematic view of a pattern after the second dry etching is as shown in FIG. 6. In FIG. 1, FIG. 2, FIG. 4 and FIG. 6, 11 denotes a base, 12 denotes a gate, 13 denotes a gate insulating layer, 14 denotes an active layer, 15a denotes a data line precursor, 15 denotes a data line, 16a Denotes a source/drain precursor, 161 denotes a source, 162 denotes a drain, 163 denotes a channel formed between the source 161 and the drain 162, 1a denotes a photoresist.
In summary, due to the limitations of the current 4-mask process, the step coverage and yield are greatly affected.